148 research outputs found
Instabilities of Electroweak Strings
We investigate the instabilities of low winding number electroweak strings
using standard numerical techniques of linear algebra. For strings of unit
winding we are able to confirm and extend existing calculations of the unstable
region in the () plane. For strings of higher winding
number we map the unstable regions for the various decay modes.Comment: Latex, 11 pages, 1 uuencoded figur
Cosmic Electroweak Strings
We examine the Standard Model field configurations near cosmic strings in a
particular class of models. This class is defined by the condition that the
generator of the flux in the string, , commutes with the Standard Model
Lie algebra. We find that if the Standard Model Higgs carries a charge
under , cosmic string solutions have Z-flux , where is any integer and is the flux of the gauge field associated with . Only the
configuration with the smallest value of is stable,
however. We argue that the instabilities found at higher are just
associated with paths in configuration space reducing by
one unit. This contradicts recent claims that the instabilities in such models
represent the spontaneous generation of current along the string. We also show
that the stable strings have no Standard Model fermion zero modes: therefore
there is no possibility of supercurrents carried by Standard Model particles in
this class of models.Comment: Latex, 13 pages, 2 uuencoded figure
Sphalerons, Antisphalerons and Vortex Rings
We present new classical solutions of Weinberg-Salam theory in the limit of
vanishing Weinberg angle. In these static axially symmetric solutions, the
Higgs field vanishes either on isolated points on the symmetry axis, or on
rings centered around the symmetry axis. The solutions represent systems of
sphalerons, antisphalerons, and vortex rings.Comment: 8 pages, 3 figures, minor corrections include
Cosmological Hydrodynamics with Multi-Species Chemistry and Nonequilibrium Ionization and Cooling
We have developed a method of solving for multi-species chemical reaction
flows in non--equilibrium and self--consistently with the hydrodynamic
equations in an expanding FLRW universe. The method is based on a backward
differencing scheme for the required stability when solving stiff sets of
equations and is designed to be efficient for three-dimensional calculations
without sacrificing accuracy. In all, 28 kinetic reactions are solved including
both collisional and radiative processes for the following nine separate
species: H, H+, He, He+, He++, H-, H2+, H2, and e-. The method identifies those
reactions (involving H- and H2+) ocurring on the shortest time scales,
decoupling them from the rest of the network and imposing equilibrium
concentrations to good accuracy over typical cosmological dynamical times.
Several tests of our code are presented, including radiative shock waves,
cosmological sheets, conservation constraints, and fully three-dimensional
simulations of CDM cosmological evolutions in which we compare our method to
results obtained when the packaged routine LSODAR is substituted for our
algorithms.Comment: Latex and postscript, 24 pages, with 6 figures. The paper is also
available at http://zeus.ncsa.uiuc.edu:8080/~abel/PGas/bib.html Submitted to
New Astronom
Gravitating Sphaleron-Antisphaleron Systems
We present new classical solutions of Einstein-Yang-Mills-Higgs theory,
representing gravitating sphaleron-antisphaleron pair, chain and vortex ring
solutions. In these static axially symmetric solutions, the Higgs field
vanishes on isolated points on the symmetry axis, or on rings centered around
the symmetry axis. We compare these solutions to gravitating
monopole-antimonopole systems, associating monopole-antimonopole pairs with
sphalerons.Comment: 7 pages, 3 figure
Primordial black holes with an accurate QCD equation of state
Making use of definitive new lattice computations of the Standard Model thermodynamics during the quantum chromodynamic (QCD) phase transition, we calculate the enhancement in the mass distribution of primordial black holes (PBHs) due to the softening of the equation of state. We find that the enhancement peaks at approximately 0.7 M-circle dot, with the formation rate increasing by at least two orders of magnitude due to the softening of the equation of state at this time, with a range of approximately 0.3 M-circle dot <M <1.4 M-circle dot at full width half-maximum. PBH formation is increased by a smaller amount for PBHs with masses spanning a large range, 10(-3) M-circle dot <M-PBH <10(3) M-circle dot, which includes the masses of the BHs that LIGO detected. The most significant source of uncertainty in the number of PBHs formed is now due to unknowns in the formation process, rather than from the phase transition. A near scale-invariant density power spectrum tuned to generate a population with mass and merger rate consistent with that detected by LIGO should also produce a much larger energy density of PBHs with solar mass. The existence of BHs below the Chandresekhar mass limit would be a smoking gun for a primordial origin and they could arguably constitute a significant fraction of the cold dark matter density. They also pose a challenge to infiationary model building which seek to produce the LIGO BHs without overproducing lighter PBHs.Peer reviewe
System size scaling of topological defect creation in a second-order dynamical quantum phase transition
We investigate the system size scaling of the net defect number created by a
rapid quench in a second-order quantum phase transition from an O(N) symmetric
state to a phase of broken symmetry. Using a controlled mean-field expansion
for large N, we find that the net defect number variance in convex volumina
scales like the surface area of the sample for short-range correlations. This
behaviour follows generally from spatial and internal symmetries. Conversely,
if spatial isotropy is broken, e.g., by a lattice, and in addition long-range
periodic correlations develop in the broken-symmetry phase, we get the rather
counterintuitive result that the scaling strongly depends on the dimension
being even or odd: For even dimensions, the net defect number variance scales
like the surface area squared, with a prefactor oscillating with the system
size, while for odd dimensions, it essentially vanishes.Comment: 20 pages of IOP style, 6 figures; as published in New Journal of
Physic
The phases of deuterium at extreme densities
We consider deuterium compressed to higher than atomic, but lower than
nuclear densities. At such densities deuterium is a superconducting quantum
liquid. Generically, two superconducting phases compete, a "ferromagnetic" and
a "nematic" one. We provide a power counting argument suggesting that the
dominant interactions in the deuteron liquid are perturbative (but screened)
Coulomb interactions. At very high densities the ground state is determined by
very small nuclear interaction effects that probably favor the ferromagnetic
phase. At lower densities the symmetry of the theory is effectively enhanced to
SU(3), and the quantum liquid enters a novel phase, neither ferromagnetic nor
nematic. Our results can serve as a starting point for investigations of the
phase dynamics of deuteron liquids, as well as exploration of the stability and
dynamics of the rich variety of topological objects that may occur in phases of
the deuteron quantum liquid, which range from Alice strings to spin skyrmions
to Z_2 vortices.Comment: 9 pages, 6 figures; v2: fixed typo
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